Motor vehicles are provided with a park brake that is usually operated by a cable. This cable is connected to a park brake actuator located inside the passenger compartment convenient to the driver. Many of these actuators incorporate a pedal lever for foot operation, while others utilize a hand lever to tension the cable to apply the park brake.
A pawl-and-ratchet or other type of latch mechanism is provided to retain the lever in a selected brake-apply position. Brake release is usually via operation of a release handle to disengage the pawl from the ratchet. A park brake actuator of this type is shown in De Leeuw et al. U.S. Pat. No. 4,612,823 and assigned to the assignee hereof.
Initial operation of the park brake actuator operating lever is at a relatively low input force as cable slack is taken up and the cable is initially tensioned. Further cable tensioning requires an increasing input force. Because the space provided for lever travel is limited, it is desirable to limit the lever travel required to fully set the park brake. It is also desirable to limit the maximum operator input force required to apply the park brake.
To accomplish this, variable ratio arrangements have been proposed. In these, the amount of cable travel per unit of lever travel decreases as the brake is applied. A park brake incorporating such a variable ratio arrangement is illustrated in Hybarger U.S. Pat. No. 3,918,321.
It has also been found that the brake-apply cable stretches with use. To accommodate this stretching, various slack take-up devices have been developed, such as the under-car compensator illustrated in Senft et al. U.S. Pat. No. 4,899,007. Another type of slack take-up device, mounted with the park brake actuator is disclosed in Porter et al. U.S. Pat. No. 4,841,798.
It would be desirable to provide a simplified park brake actuator which provides both the variable ratio and slack take-up features.